Answer to L.T.T. – 08

In this month’s LTT by Lionel Griache, it was important to not ignore the extra information provided by the manager of the Postpaid Billing-System: an increase of processing-exceptions, in particular due to unknown/inactive A-Numbers.

With the information provided, here’s how the proposed answers could be evaluated:

1. Because of a crash & recovery of the mediation application, the Revenue-Assurance system received duplicate CDRs, artificially reporting higher number of SMS on the SMSc graph.

Not Likely. If the RA-System was the only application to receive duplicates, the Billing-System would not have any reason to report an increase in processing-exceptions for this revenue-stream. If the Billing-System had also received the same duplicates, you would indeed potentially see an increase in processing-exceptions but the errors reported would not be about an increase of SMS that can’t be associated to any active subscriber. The duplicate CDRs have, by definition, the same values of the original CDRs and have therefore no reason to be rejected on processing unless the Billing-System is smart enough to detect the duplication. In that case, the billing-system would generate specific errors (“duplicate-CDRs” error-message), not an unknown/disconnected A-Number error.

2. This is a classical revenue leak. The Billing-System didn’t receive all the files produced by the SMSc during the period. Collecting the files and processing them in Billing will allow to recover the revenue.

Not likely. This is not a typical revenue-leakage scenario for different reasons:

a) Uncollected & unprocessed files would not generate an increase in exceptions in the Billing system. You’d see a gap indeed, but no associated increase in exceptions.
b) The Billing graph is overall showing a regular profile compared to the previous days of the week, indicating that the usual expected volume of billable traffic has correctly been received and processed in Billing. In this case, the gap seems to represent extra-traffic compared to the usual volume of billable traffic.
c) Usage-Files usually contain CDRs that cover a continuous period in time. Missing them in the processing would create an irregular profile and not show, like here, a smooth profile, in line with a typical day.

3. This is a possible case of fraud. The fraudsters are generating SMS using the Postpaid number-range as the originating number.

Possible. This is a scenario consistent with the graph and the information provided by the Billing-Manager.

a) The SMSc is reporting the expected volume of billable traffic (compared to previous days) but it is also reporting an extra, unexplained, volume of traffic that could be caused by fraud.

b) If Fraudsters generated plausible A-numbers for their SMS, using a number-range reserved for postpaid numbers, it is plausible to see these SMS in the RA system as valid Postpaid SMS. It is then also plausible for the mediation system to send these SMS to the Billing system. This last-one rejected the SMS because the A-numbers couldn’t be matched to any valid subscriber, therefore generating higher exceptions, precisely about inexistent A-numbers.

4. The team managing the Billing-System probably forgot to configure the new short-code that the marketing team launched at the start of the week

Not likely. On one side, adding a new short-code for a marketing campaign or a new service can indeed generate extra traffic which could explain the extra volume on the SMSc. Not configuring the new Short-Code in the Billing-System would also generate extra exceptions. However, these exceptions would be about an unknown B-number, and not about unknown or disconnected A-Numbers. These SMS would still be associated to valid subscribers and the error would instead be about a missing B-number or missing rating rule.

In addition, in this scenario the gap would be on-going and not stop after 24 hours. It would stop after 24 hours only if the billing-team finally configured the extra short-code after 24 hours but then you’d expect the gap to disappear after exceptions are re-processed.

5. The extra number of SMS is simply due to the Final of the BasketBall World Championship taking place in the country this week. Roaming visitors are generating a high number of SMS and their A-number was simply not recognized by the Postpaid Billing System.

Not likely. Traffic generated by roaming visitors are not sent to the Postpaid Billing System but instead sent via TAP files to the clearinghouses/partners for compensation. This scenario would therefore not generate any additional exceptions in the billing system. The graph is also supposed to show SMS produced by Postpaid subscribers based on number-range analysis which would not cover traffic generated by a visitor roaming with a different non-local number.

6. The SMSc had technical issues during the period and it took an average of 3 attempts for the SMSc to deliver each SMS, generating a much higher graph on the SMSc than on the Billing System.

Not likely. SMSCs usually don’t produce a CDR for each delivery attempt. For each SMS sent, you’re getting only 1 CDR with the number of attempts and a code indicating if the SMS was successfully delivered at the end or not. This technical difficulty (or delay in delivering the SMS) is therefore not likely to generate any increase in CDRs on the SMSc. Also, in this scenario, you wouldn’t have an increase in exceptions in the Billing-System, especially not with for the kind of error reported.

The most likely answer was therefore #3! Congrats to Inguna Ievina for providing the first correct answer. The next LTT will be published on Monday 16th September.